A Pilot Study of Cognition Among Hypoparathyroid Adults

Hypoparathyroidism: changes in brain structure, cognitive impairment, and reduced quality of life

Hypoparathyroidism (HypoPT) is a disease with no/or inadequate production/secretion of parathyroid hormone (PTH) from the parathyroid glands. Low levels of PTH result in hypocalcemia, which is often treated with calcium supplementation and active vitamin-D analogs. However, increasing evidence suggests that HypoPT has a profound impact on several organ systems. Quality of life (QOL) is reduced in patients with HypoPT, partly due to symptoms related to the central nervous system-including subjective feelings of confusion, a reduced ability to focus and think clearly (ie, "brain fog"). However, the extent to which these complex symptoms relate to quantifiable changes in patients' cognitive performance as determined by neuropsychological tests remains unclear. The brains of HypoPT patients may reveal tissue calcifications, but the extent to which long-term brain exposure to low PTH levels and/or changing calcium levels affects brain structure is unknown. In a cross-sectional study, we investigated PTH levels, QOL, cognitive impairment, and brain structure in well-treated post-surgical and non-surgical hypoparathyroid patients compared with healthy controls. QOL was quantified by the SF36v2, WHO-5 wellbeing Index, and two disease-specific questionnaires-the HPQ28 and Hypoparathyroidism Symptom Diary. Cognitive functions were tested using comprehensive neuropsychological. Brain structure was quantified by morphological analyses of magnetic resonance imaging images. We found reduced QOL and cognitive functioning in terms of processing speed, executive functions, visual memory, and auditory memory in HypoPT. Furthermore, HypoPT revealed a reduced volume of the hippocampus-and the size of the thalamus in postsurgical patients was associated with the disease duration. Importantly, patients reporting severe brain fog had a smaller hippocampus than those with less brainfog. HypoPT is associated with quantifiable cognitive deficits and changes in brain structure that align with patient symptoms. Our exploratory study warrants further studies of the neurobiological impact of PTH and of the impact of PTH replacements therapy on patients' cognitive functioning.

The Role of the Patient Partnership in Designing Research on Neuropsychiatric Issues in Hypoparathyroidism

Hypoparathyroidism is a rare endocrine disease that is associated with hypocalcemia and insufficient parathyroid hormone (PTH) levels. Neuropsychiatric complaints are common in hypoparathyroidism. Yet there is a large knowledge gap in our understanding of cognitive dysfunction in hypoparathyroidism and partnering with patients is essential for filling this hole. Input from hypoparathyroid patients is needed to define objective, performance-based cognitive impairments. Creating patient advisory boards that provide input for planning clinical trials would enable patient perspectives to be shared. This would ensure that meaningful, standardized neuropsychological instruments that prioritize patients' cognitive concerns are selected. Patient partnership is also needed to understand the wide inter-individual variability of cognitive symptoms in hypoparathyroidism, as well as mechanisms aside from calcium shifts that might explain cognitive symptoms, such as low PTH itself, alterations in brain structure, or other hypoparathyroidism-associated comorbidities. With new PTH replacement therapies on the horizon, patient input about studying how these therapies impact, and maybe even reverse, cognitive impairment will also be critical. Ultimately, the inclusion of patient partners in hypoparathyroidism research will advance the design of neuropsychiatric studies and generate key input for understanding how to reduce the burden of this disease.

Normative Reference Values for Crystallized-Fluid Discrepancy Scores for the NIH Toolbox Cognition Battery

INTRODUCTION

The purpose of this study was to translate NIH Toolbox Cognition Battery (NIHTB-CB) Crystallized-Fluid discrepancy scores into research and clinical practice with adults by providing normative data for discrepancy scores for both age-adjusted standard scores (SSs) and demographically adjusted T-scores.

METHOD

We included adult participants from the NIHTB-CB standardization sample who denied having neurodevelopmental, medical, psychiatric, or neurological conditions (n = 730; M = 47.4 years old, SD = 17.6, range: 18-85; 64.4% women; 63.1% White). Descriptive statistics were calculated for the Fluid and Crystallized composite scores and Crystallized-Fluid discrepancy score, along with correlations between the composite scores and reliability estimates of the discrepancy score. Percentiles were calculated for the discrepancy score, with stratifications by the gender, education, and Crystallized composite for the age-adjusted SSs and demographically adjusted T-scores (T).

RESULTS

Crystallized-Fluid discrepancy scores ranged from -40 to 44 (M = -0.63, SD = 14.89, Mdn = -1, interquartile range [IQR]: -11 to 10) for age-adjusted SSs and from -29 to 27 (M = -0.39, SD = 10.49, Mdn = -1, IQR = -8 to 7) for demographically adjusted T-scores. Crystallized-Fluid discrepancy scores of SS = 15 and T = 11 were at the 16th percentile (1 SD below the mean) and discrepancy scores of SS = 21 and T = 15 were at the 7th percentile (1.5 SD below the mean).

CONCLUSIONS

Crystallized-Fluid discrepancy scores may be, with future research, a useful within-person interpretive approach for detecting a decline from pre-injury or pre-disease levels of cognitive functioning. These normative reference values assist clinicians and researchers in determining the frequency at which given Crystallized-Fluid discrepancy scores occurred among healthy adults in the normative sample.

Parathyroid Hormone (PTH)-Related Peptides Family: An Intriguing Role in the Central Nervous System

Parathyroid Hormone (PTH) plays a crucial role in the maintenance of calcium homeostasis directly acting on bone and kidneys and indirectly on the intestine. However, a large family of PTH-related peptides exists that exerts other physiological effects on different tissues and organs, such as the Central Nervous System (CNS). In humans, PTH-related peptides are Parathyroid Hormone (PTH), PTH-like hormones (PTHrP and PTHLH), and tuberoinfundibular peptide of 39 (TIP39 or PTH2). With different affinities, these ligands can bind parathyroid receptor type 1 (PTH1R) and type 2 (PTH2R), which are part of the type II G-protein-coupled-receptors (GPCRs) family. The PTH/PTHrP/PTH1R system has been found to be expressed in many areas of the brain (hippocampus, amygdala, hypothalamus, caudate nucleus, corpus callosum, subthalamic nucleus, thalamus, substantia nigra, cerebellum), and literature data suggest the system exercises a protective action against neuroinflammation and neurodegeneration, with positive effects on memory and hyperalgesia. TIP39 is a small peptide belonging to the PTH-related family with a high affinity for PTH2R in the CNS. The TIP39/PTH2R system has been proposed to mediate many regulatory and functional roles in the brain and to modulate auditory, nociceptive, and sexual maturation functions. This review aims to summarize the knowledge of PTH-related peptides distribution and functions in the CNS and to highlight the gaps that still need to be filled.